Parallel manual transmissions, also called twin-clutch transmissions, are drawing increasing interest because they enable the realization of an automatic transmission that can be operated without interruptions in propulsive power, are similar in design to a mechanical manual transmission, and have correspondingly low friction losses.
Ordinarily, four-wheel drive systems are designed such that a transfer case is connected to a manual transmission, such as a parallel manual transmission, and a drive shaft for the front axle extends outward from the transfer case, and parallel to the main gearbox, so that little space remains for actuation of the transmission and clutch, or for an optional electric motor. Having such little space presents a number of difficulties and therefore, it is desirable for a system to be designed with increased space.